This application is based on Patent Application Nos. 300,208/1997 filed on Oct. 31, 1997 in Japan and 168,750/1998 filed on Jun. 16, 1998 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus such as a color copying apparatus and a color correction method. More particularly, the invention relates to color correction performed in a color copy machine, a facsimile machine having a color copy function, or the like.
2. Description of the Related Art
Such color copy machine or facsimile machine integrally includes a reading system and a printing system. Conventionally, color correction for a color image output in these apparatus is typically performed in respective of the reading system and the printing system independently. For example, for the reading system, the color correction is performed by using a tool on a personal computer (hereinafter, also called xe2x80x9cPCxe2x80x9d simply) connected to the color copy machine or the like, using together with a color chart for color correction. On the other hand, also in the printing system, the color correction is performed by using the tool on the PC, similarly. On the basis of these color correction, total color correction is finally performed including the reading system and the printing system.
Not only in a printer but also in these copy machine and facsimile machine performing color output, the printing system using an ink-jet method has been generally used. This ink-jet method is designed to perform printing by forming dots on a printing paper with an ink by ejecting the ink toward the printing paper, and has an advantage in capability of printing on basically any printing paper as long as the ink can be fixed. For instance, a plain paper which is widely used in general, an OHP sheet coated an ink receptacle layer on a plastic sheet, a cloth and the like have been known to be usable.
As set forth above, in an ink-jet system, wide variation of printing medium can be used. In this point, variation of the printing medium which a user of the printer or the like wants to use for printing, is increasing. Even limiting for the case of using the plain paper, there are many kinds of plain paper. In this case, the plain papers of respective kinds are different in property on the ink, such as fixing ability of the ink.
The conventional color correction per se and the color correction which is performed in a color copy system employing a printing apparatus of the ink-jet method, have following problems.
The standard conventional color correction is independently performed for the reading system and the printing system, respectively. Therefore, the color correction performed by employing the tool on the PC or the like is relatively complicate and requires long time. Furthermore, since various tools for the color correction or charts for evaluation are used in the conventional color correction, a cost for performing the color correction may become relatively high.
Furthermore, when the total color correction for both of the reading system and the printing system in a final stage on the basis of the color correction performed individually in the reading system and the printing system, a process of the color correction is not so easy. In addition, a decrease of a throughput may be caused in outputting a color copy image due to such complicated color correction.
In addition to the problem encountered by the conventional color correction per se, as a problem in the color correction in the ink-jet copy system, there is a problem in the printing medium to be employed upon printing a patch used for the color correction. More specifically, when a kind of the printing medium on which the patch is printed is different, an ink absorbing property is also different in accordance with the kind of the printing medium. In this case, for example, when the patch used for the color correction is printed on the printing medium having a low ink absorbency, a coloring agent, such as dye or the like in the ink ejected for printing the patch does not penetrate into the printing medium to be remained in a shallow portion or on a surface of the printing medium. As a result, density read with respect to such patch becomes relatively high. Particularly, upon printing of the patch, a predetermined region of the patch is often printed at a duty of 100%. Therefore, a density difference depending upon an absorbing ability of the ink to the printing medium becomes significant. Furthermore, when the patch of blue as an intermediate color is output with a cyan ink and a magenta ink, for example, the foregoing duty becomes 200% to make difference of the density depending upon the absorbing ability of the ink to the printing medium more significant.
Further, as another factor to cause increasing of the density of the patch with respect to the absorbency of the ink set forth above, it is known that in the case of using the printing medium having the low absorbency in a direction perpendicular to the surface of the printing medium, the ink may spread along the surface of the printing medium instead of penetrating in a thickness direction of the printing medium to easily cause bleeding. As a result of this, the ink dot tends to cover entire pixel and thus tends to also make the density high.
It should be noted that when the printing medium having the high ink absorbency is used, the density tends to be lower. Even in this case, problem can be encountered in the color correction.
As set forth above, in the case that the read density of the patch becomes different depending upon the absorbing ability to the ink, and the color correction is performed by reflecting the read density as is on a process of color correction, at the lower ink absorbency of the printing medium to be used for printing of the patch, printing based on a result of the color correction may be performed with higher density than the essentially proper density or performed in different color. Particularly, the printing density the patch of the intermediate color, at which the duty normally becomes as high as 200%, becomes significantly high or cause the difference of color to degrade quality of the printed image where poor balance in the density or color in the overall printed image occurs.
An object of the present invention is to provide an image forming apparatus and a color correction method which can easily perform color correction in a short period by performing the color correction automatically.
Another object of the present invention is to provide an image forming apparatus and a color correction method in which printing with a predetermined production color is performed by a printing portion of the image forming apparatus, a printed image of the predetermined production color is read by a reading portion of the same image forming apparatus, and content stored in a table which is used for printing of a color image is updated with a color component obtained based on a read result by the reading portion so as to perform color correction, so that an image printed by the printing portion based on a result read by the reading portion which has been subjected to the color correction can match an image read by the reading portion and thereby a color of an original image can be faithfully reproduced.
A further object of the present invention is to provide an image forming apparatus and a color correction method which can easily perform color correction in a short period by automatically performing the color correction and can perform printing with an appropriate balance of density or color with respect to respective production colors as a result of the color correction.
A still further object of the present invention is to provide an image forming apparatus and a color correction method in which printing with a predetermined production color is performed by a printing portion of the image forming apparatus, a printed image of the predetermined production color is read by a reading portion of the same image forming apparatus, and content stored in a table which is used for printing of a color image is updated with a color component obtained based on a read result by the reading portion so as to perform color correction, so that an image printed by the printing portion based on a result read by the reading portion which has been subjected to the color correction can match an image read by the reading portion and thereby a color of an original image can be faithfully reproduced, wherein since the printing with the predetermined production color for the color correction is performed at a print duty which is previously set, printing can be performed with the printing duty lowered correspondingly even when density read by the reading portion tends to high due to influence of the printing medium, and thereby the read density can be appropriate to make the content stored in the table corresponding thereto appropriate.
In the first aspect of the present invention, there is provided a color correction method for performing color correction of a system using a table storing m-valued color component data corresponding to a production color which can be printed by a printing portion of the system which portion performs printing on a basis of n-valued output color component data (m greater than n), the table being used for conversion process of print data into n-valued data the method comprising the steps of:
receiving an execution command of a color correction process;
printing the predetermined production color using the output color component data corresponding to the predetermined production color, by means of the printing portion;
reading a result of printing of the predetermined production color, by means of a reading portion; and
updating the color component data, which is stored in the table and corresponds to the predetermined output color, by the color component data obtained from a read result of the reading step.
In the second aspect of the present invention, there is provided an image forming apparatus having a reading portion and a printing portion, the printing portion performing printing on a basis of a result of reading by the reading portion, the apparatus comprising:
table means for storing color component data for each color component corresponded to a production color which can be printed by the printing portion, the table means is used for generating output color component data used by the printing portion on a basis of color component data obtained from a result of reading by the reading portion upon printing of a color image; and
color correction control means for making the printing portion perform printing of a predetermined production color using the output color component data corresponding to the predetermined production color and making the reading portion perform reading of a result of printing of the predetermined production color, and updating storage data of the table means corresponding to the predetermined production color by the color component data obtained from a result of reading by the reading portion.
In the third aspect of the present invention, there is provided a storage medium which is connected to an information processing apparatus and a program stored in which is readable by the information processing apparatus, the printing medium storing a process, wherein the process is a color correction process of a system using a table storing m-valued color component data corresponding to a production color which can be printed by a printing portion of the system which portion performs printing on a basis of n-valued output color component data (m greater than n), the table being used for conversion process of print data into n-valued data, the method comprising the steps of:
receiving an execution command of a color correction process;
printing the predetermined production color using the output color component data corresponding to the predetermined production color, by means of the printing portion;
reading a result of printing of the predetermined production color, by means of a reading portion; and
updating the color component data, which is stored in the table and corresponds to the predetermined output color, by the color component data obtained from a read result of the reading step.
The above and other object, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.